The invention relates to a multi-domain liquid-crystal display device comprising two substantially parallel substrates which are provided with an electrode layer and an orientation layer, a layer of a nematically ordered liquid-crystalline material containing a chiral dopant being sandwiched between said substrates, and said layer being structured such that the pixels of the layer are composed of at least two types of sub-pixels in which the twist senses of the liquid-crystalline material are mutually opposite. The invention also relates to methods of manufacturing such a display device. Display devices of this type can be employed, for example, in monitors and TV receivers as well as in measuring equipment.
Display devices of the above-mentioned type are known per se, for example, from the international patent application with publication no. WO 95/18989. In such display devices, the individually drivable pixels are composed of two sub-pixels having an opposite twist sense. In the one type of sub-pixel, the liquid-crystalline material has an anti-clockwise twist sense, while in the other type of sub-pixel the liquid-crystalline material has a clockwise twist sense. If desirable, each of the sub-pixels may itself be composed of two further sub-pixels by providing two regions in which the liquid-crystalline molecules have a different tilt direction. In this case, four different types of sub-pixels can be distinguished in the display device.
An important advantage is achieved by subdividing the pixels into two or even four types of mutually different sub-pixels. It has been found that this causes the viewing angle dependence of the device to be substantially improved. The viewing angle dependence of a display device is to be taken to mean the degree of contrast, grey-scale inversion, discoloration and brightness variation of the device as a function of the angle from which the device is viewed. In general, the aim is to minimize the viewing angle dependence. This means that the intended display device should demonstrate, as a function of the viewing angle, a high contrast, a proper grey-scale distance, little discoloration as well as a small brightness variation.
The known display device has an important drawback which manifests itself, in particular, when the display device is mass-produced. For example, in the manufacture of the known devices, a number of rubbing steps and/or lithographic steps are necessary to provide the orientation layer with the desired structure at the level of the sub-pixels. Such steps are very unattractive from the production-technical point of view.